System and method for treating water systems with high voltage discharge and ozone

ABSTRACT

A system and method for treating flowing water systems with a plasma discharge to remove or control growth of microbiological species. The system and method protect other components of the water system from being damaged by excess energy from the electrohydraulic treatment. The system and method also recycle ozone gas generated by a high voltage generator that powers the plasma discharge to further treat the water. A gas infusion system upstream of or inside a plasma reaction chamber may be used to create fine bubbles of ozone, air, or other gases in the water being treated to aid in plasma generation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/260,605filed on Apr. 24, 2014, which claims the benefit of provisional U.S.Application Ser. No. 61/818,229, filed on May 1, 2013.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to a system and method for treating flowing watersystems using a high voltage discharge to generate plasma and using theozone by-product from the high voltage generation, particularly usefulin treating cooling tower or other recirculating or closed-loop systems.

2. Description of Related Art

Anthropogenic water systems are critical components commonly found inmost of the world's energy producing facilities, industrial andmanufacturing plants, hospitals, and other institutional complexes andbuildings. These systems consume around 700 billion gallons of waterannually with a cost of $1.8 billion in make-up water and sewagehandling costs alone. All of these anthropogenic water systems requiresome form of treatment, either chemical or non-chemical, to control thebuild-up of scale, biofilm and other corrosion by-products on theimportant heat transfer surfaces that are necessary for efficient systemoperation.

For water systems involving heat exchange, such as cooling towers andboilers, effective treatment to remove these contaminants and to prolongthe amount of time before the systems are re-contaminated can savesignificant amounts of money. An effective and thorough treatment maysave costs for labor and treatment chemicals by reducing the frequencyof periodic treatments or reducing the amount of chemicals needed forroutine maintenance and/or periodic treatments. Such a treatment mayalso save on energy costs through the operation of clean heat exchangesurfaces. Fouling of heat exchange surfaces costs U.S. industry hundredsof millions of dollars every year and is directly related to an increasein energy consumption of almost 3 quadrillion Btus (quads) annually.

To maximize the water usage and minimize waste, many of these systemsemploy a series of chemical treatments that protect the system againstscaling, biofilm formation, and corrosion. These chemical treatmentsallow the water to be reused and recycled a number of times before itbecomes necessary to discharge the water and replace it with freshwater. Increasing the duration for which the water may be circulatedsignificantly reduces the amount of water that is discharged to thesewage system and minimizes the amount of make-up water that is neededto replace the bleed off. However, many chemical treatment compositionsand methods may damage the components of the water system being treatedas the chemicals used are highly corrosive. There is also anenvironmental down side to harsh chemical treatments, including growingconcern over the formation of toxic disinfection-by-products such astrihalomethanes, haloacetonitriles, and halophenols that have beenidentified in the discharge water being released into the environment.It is estimated that there are 536 billion pounds of water treatmentchemicals discharged annually as a result of cooling tower treatments,which may impact a variety of species living in or near areas andwater-ways receiving the discharge or bacterial components of sewagetreatment plants receiving the discharge.

In an attempt to minimize the environmental impact associated with somechemical treatments, many water treatment companies, and moreimportantly their customers, are looking to use non-chemical based watertreatment technologies to maintain the performance of their systems.There are currently about 30 non-chemical treatment devices or waterconditioning technologies that are commercially available for use inboth commercial and residential water systems. These systems can bedivided into three categories: (1) Indirect chemical producers that usea benign or safe chemical additive such as air or salt to produce thebiocide. These systems include ozone generators and electrochemicalhypochlorite generators and mixed oxidant generators. (2) Directchemical producers that generate the active chemical species from directinteraction on the water. These devices use mechanical processes, suchas hydrodynamic cavitation or sonic cavitation, to produce hydroxylradicals along with localized areas of high temperatures and pressuresin the water. Other types of devices that would fit into this categoryare ultraviolet light systems. (3) Electrical and Magnetic devices,including plasma generation, use induced electrical and magnetic fieldsto induce ion migration and movement that can result in cell deaththrough electroporation, or ion cyclotron resonance effects within thecell wall. Out of all of these technologies the electrical and magneticdevices are the most common; however, they are the technologies thathave the least rigorous scientific support. The direct and indirectchemical approaches have more scientific credibility; however, thisgreater understanding may have limited their potential applications andhence they have not been able to capture a larger portion of the marketshare.

The application of high voltage discharge and generating plasma withinwater is known in the prior art. For example, an article published by B.R. Locke et al. (Ind Eng. Chem Res 2006, 45,882-905) describes electrodeconfiguration and geometry, the pulsed arc vs. pulsed corona, and thechemical species that are formed during an electrohydraulic dischargeand non-thermal plasma in water discharge process. The article addressesmany of the fundamental issues related to using this technique for watertreatment, but it fails to address the practical applications related towater treatment in an industrial, commercial, or residentialenvironment, especially related to the need for multiple ground pointsto minimized the effect of the electromagnetic radiation released intothe water and surrounding atmosphere.

It is also know to use ozone gas to treat water. For example, in anarticle by Gupta et al. (S. B. Gupta, IEEE Transactions on PlasmaScience, 2008, 36, 40, 1612-163) the use of an advanced oxidationprocess resulting from pulsed discharges in water is described. Theprocess described by Gupta uses oxygen gas or ozone gas supplied intothe discharge reactor from secondary independent sources (and not fromthe high voltage generator). They also report that system output andperformance is highly dependent on solution conductivity. For systemswhere water conductivity can be high, such as in cooling tower andclosed loop applications, higher voltage discharges are needed and thisin turn creates problems with increased electromagnetic radiation.

There are also several prior art patents or published patentapplications that address plasma generation for various purposes,including water treatment or purification, such as U.S. PatentApplication Pub No. 2009/0297409 (generation of flow discharge plasmasat either atmospheric or higher pressures), U.S. Patent Application PubNo. 2006/0060464 (generation of plasma in fluids, in particular formedwithin the bubbles generated and contained in an aqueous medium), U.S.Pat. No. 6,558,638 (using high voltage discharge to treat liquids, whileincorporating a gas delivery means for generating bubbles in thedischarge zone), and U.S. Patent Application Pub No. 2010/0219136(pulsed plasma discharge to treat fluid such as water at a flow rate of5 gpm while consuming only 120-150 Watts of power).

The prior art teaches that high voltage discharges in water can generatechemically active species, exhibit physical effects, and control waterchemistry. However, the known prior art does not address the how toapply this technology of using plasma discharge to treat larger volumesof flowing water in an industrial, commercial or residential settingover longer periods of time without damaging other components of thewater system, including the controllers and monitors that are needed forscale and corrosion control, blowdown, and water conservation measures.

SUMMARY OF THE INVENTION

This invention relates to a system and method using non-chemicaltechnologies to treat flowing water systems, such as cooling towers andclosed-loop or recirculating water systems. This treatment involvesgenerating a high frequency and high voltage discharge between twoelectrodes submerged in the water being treated. With each dischargebetween the electrodes there is a number of long lived oxidativechemicals (ozone, hydrogen peroxide) and short lived oxidative chemicals(super oxides, hydroxyl radicals, and hydrogen radicals) generated, UVradiation is also generated, together with sonic shockwaves. Theseeffects are well known in the prior art. However, it is not previouslyknown to utilize an electromagnetic or electrolysis system that capturesthe excess energy produced by the high voltage discharge (which isnormally wasted). According to one embodiment of the invention, thesystem uses this excess energy to further condition and treat the waterby allowing the current to flow through wire loops connecting watersystem piping to a ground to generate a magnetic field in the water.This magnetic field has been shown to have a beneficial effect in watertreatment and avoids the damaging effects of the large amounts ofelectromagnetic radiation throughout the entire water system have on theelectronic control systems used to measure conductivity, pH, biologicalactivity, as well as to control pumps and other critical systemcomponents that are typically found with systems that directly generatea high voltage discharge into a water supply.

To use a high voltage discharge without having multiple ground points inthe water or adequate shielding around the high voltage componentsseverely limits the applicability of the existing prior art. Anotherembodiment of the invention includes the use of a micro-bubble generatorthat introduces a fine stream of micro-bubbles into the high voltagedischarge chamber. In order to maximize the reaction area for the highvoltage discharges in highly conductive water power supplies with thecapability of generating over 200 kV are required. A by-product in theoperation of these power supplies is the production of ozone gas thatmust be removed from the system. Our patent teaches that this ozone gasproduced as a by-product of the high voltage power supply can beintroduced into the high voltage chamber as a fine dispersion ofmicro-bubbles to make a zone where oxidation reactions are enhanced.Additionally the high voltage chamber can incorporate a fluid handlingsystem that generates micro-bubbles within the high voltage dischargezone through sonication or hydrodynamic cavtation. Finally our patentteaches using a pulsed high voltage discharge regimen where the highvoltage discharge can be applied in specific time increments to preventover heating of the water, wiring, or other critical power supplycomponents.

BRIEF DESCRIPTION OF THE DRAWINGS

The apparatus of the invention is further described and explained inrelation to the following drawings wherein:

FIG. 1 is a schematic view of one preferred embodiment of a systemaccording to the invention;

FIGS. 2A and 2B are graphs showing electromagnetic fields measured inone experiment when an embodiment of the invention was not applied;

FIG. 3 is a graph showing electromagnetic fields measured in anotherexperiment using a preferred embodiment of the invention;

FIG. 4 is a schematic view of another preferred embodiment of a systemaccording to the invention;

FIG. 5 is a schematic view of another preferred embodiment of a systemaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of a treatment system according to the inventionis depicted in FIG. 1. Treatment system 10 preferably comprises a gasinfusing system 28, a plasma reaction chamber 36, a high voltagegenerator 40, power system 46, and various component protection devices.Treatment system 10 is easily added to an existing water system 12.Water system 12 can be any residential, commercial or residential watersystem, particularly those used for cooling applications andrecirculated water systems, such as cooling towers. Water system 12includes well known components that are not depicted in FIG. 1. A waterstream 14 from the water system 12 being treated passes through varioussensors 16 commonly used in monitoring water systems, such as pHsensors, temperature, and conductivity. Depending on the size of thewater system 12 and volume of water flowing through the water system 12,all of the water in the system may pass through the treatment system 10or only a portion or side stream may pass through treatment system 10.

Water stream 18 preferably flows through gas infusing system 28, whichinfuses water stream 18 with fine bubbles of air and/or gas. Preferably,gas infusing system 28 comprises one or more micro-bubbler devices 20,where air or gas 22, reactive gas 26, and/or ozone 30 are introducedinto the water stream as fine bubbles upstream of plasma reactionchamber 36. Reactive gases, such as ozone, mono-atomic oxygen,meta-stable singlet delta oxygen, vapor phase hydrogen dioxide, chlorinegas, chlorine dioxide gas, may also be used to achieve maximum removalof microbiological species from water system 12. The use and selectionof such gases will depend on water conditions within water system 12. Itis not required to add air, ozone, or other gas streams to water stream18, or that such be added as micro-bubbles, but the micro-bubbles aid inplasma generation and the ozone gas or reactive gas also serve to treatthe water of the water system. If bubbles are added, stream 24, infusedwith bubbles feeds plasma reaction chamber 36, otherwise stream 18 feedsplasma reaction chamber 36.

In one preferred embodiment gas infusing system 28 comprises a venturisystem for infusing a fine bubble dispersion of air/gas, reactive gas,and/or ozone into water stream 18 to produce water stream 24. Theventuri input is located upstream of the high voltage reaction chamber36 and introduces micro-bubbles of one or more of these gases into thehigh voltage discharge within the reaction chamber 36. In anotherpreferred embodiment the micro-bubbles are generated by incorporating ahydrodynamic cavitation system that introduces a highly dispersedsuspension of micro-bubbles produce by the hydrodynamic cavitationprocess into a reaction zone within reaction chamber 36. In a thirdpreferred embodiment, a venturi system and hydrodynamic cavitationsystem are used together. The combination has the advantage ofgenerating a synergistic environment for optimized reaction kinetics andactive species generation. In a fourth preferred embodiment, the highvoltage reaction chamber 36 could be coupled with a plurality ofsonicating probes that could generate micro-bubbles in situ within ahigh voltage discharge zone within chamber 36, again providingsynergistic reaction performance. Finally in a fifth preferredembodiment, one or more of these gases could be venturied into the highvoltage reaction zone together with the micro-bubbles being generated bythe sonicating probes. The introduction of micro-bubbles using any ofthese systems or devices, the components and applications of which arewell known in the art, further aid in plasma generation because thedielectric breakdown strength of air is less than that of water. As theplasma breakdown is initiated in air, ionized electrons from the airwill then carryover and begin electron ionization in the watermolecules.

Reaction chamber 36 comprises a sealed, water-tight housing 35surrounded and shielded by an inner dielectric barrier layer 34 a andouter ground shield 34 b. The dielectric barrier 34 a is anon-conductive layer that prevents arcing to the ground layer 34 b,which is a conductive outer layer tied to the ground. The dielectricbarrier 34 a and ground shield 34 b reduce electromagnetic interferencesradiating from the reaction chamber 36. If reaction chamber 36 is notshielded, sensitive electronic equipment may be damaged by the plasmagenerated within the chamber 36. Within reaction chamber 36 are disposeda high voltage electrode and a ground electrode which generate a plasmadischarge within chamber 36 as voltage generated in high voltagegenerator 40 is transmitted to the high voltage electrode within chamber36. These components for generating a plasma discharge are well known tothose of ordinary skill in the art. The shape and configuration ofreaction chamber 36, housing 35, and the high voltage and groundelectrodes within reaction chamber 36 are not critical and any knownshape and configuration may be used. Another ground 48 is also disposedin contact with ground layer 34 b surrounding housing 35, which isneeded to generate the plasma discharge in reaction chamber 36. A highlyinsulated high voltage wire 38 connects the high voltage generator 40with the high voltage electrode in reaction chamber 36. Wire 38 ispreferably insulated with a high strength dielectric to prevent arcingto other electronic devices, metal structures, or people/operators.Treated water stream 50 exits the reaction chamber 36 and returns tosump 54 (particularly where water system 12 is a cooling tower) or othercomponents or piping of water system 12 to be recirculated through thesystem. Inlet and outlet couplings for water streams 24 and 50 into andout of chamber 36 should be grounded.

High voltage generator 40 may generate a high frequency, high voltagedischarge that exceeds 200 kV on each discharge step. The high voltagegenerator 40 preferably comprises a Marx ladder or Marx generator 42disposed within a spark gap chamber 41 within an outer housing 43 thatincludes a dielectric barrier to isolate the Marx ladder 42 from thesurrounding environment and prevent arcing from the internal componentsto nearby metal structures, electrical outlets, and other monitoring andcontrol systems. To be effective in treating conductive waters similarto those seen in traditional cooling towers or closed loop systems, thehigh voltage generator 40 is preferably capable of a voltage output of200 kV for an electrode gap of around 5 mm between the high voltagedischarge electrode and the ground electrode in the reaction chamber 36.Although other gap distances may be used with modifications that wouldbe understood by one of ordinary skill in the art, a gap distance ofaround 5 mm is preferred. This is preferred because a larger gapdistance requires an increase in output voltage, which can introduceadditional issues, such as component failure in the high voltagegenerator 40, and a smaller gap distance reduces the volume of waterbeing exposed to the plasma discharge.

In one preferred embodiment, the high voltage generator 40 comprises astage 1 low voltage component that takes the 110V output from a typicalwall outlet and generates a 40 kV DC signal. This is achieved by a ZeroVolt switching circuit that pulses the input from a flyback transformer.The number of turns on the transformer can be increased or decreased tochange the output voltage of the flyback transformer. An advantage ofusing a Zero Volt Switching driver circuit is that it features a highnoise immunity, that is not susceptible to electromagnetic interferencethat is created in pulsed power systems. Digital or other circuits canalso be used, but they are more sensitive to outside interferencegenerated by the plasma reaction chamber 36 than a Zero Volt Switchingdriver. To protect the electronics from the high voltage output this isconstructed as a separated shielded entity. The signal from the stage 1low voltage component is used to charge a capacitor bank in the Marxgenerator 42, which has the capacitors assembled in parallel. When thecapacitor bank reaches the discharge limit, it triggers a cascadingdischarge event between spark gaps in a Marx ladder so as the terminalvoltage is greater than 200 kV between the discharge and groundelectrode.

Air pumps 44 or other devices to pressurize or blow air are preferablyintegrated into high voltage generator 40, but may also be external togenerator 40 and connected with appropriate conduit to permit air flowinto generator 40. Air pumps 44 blow air through the high voltagegenerator 40 to quench the electrodes of the Marx ladder 42, which aidsin increasing electrode lifetime. Air pumps 44 flush air across theelectrodes and out of the spark gap chamber 41. Ozone gas 30 generatedfrom the spark gap chamber 41 is withdrawn from high voltage generator40 and preferably recycled back to be injected or infused into waterstream 18 to provide further water treatment. Ozone gas generated fromthe Marx ladder is typically considered a waste product, but it isbeneficially used according to the invention as a source of watertreatment. Most preferably, the ozone gas 30 is venturied into waterstream 18 at or near an inlet into reaction chamber 36. This permits theintroduction of ozone into the water supply and also aerates the waterstream 18 with fine micro-bubbles to form feed stream 24.

Treatment system 10 also comprises a power system 46 and variousprotective devices to protect the components of the water system fromexcess voltage produced. Power system 46 preferably comprises anuninterruptible power supply or isolation transformer, which reduces anytransient voltage spikes from entering the power supply of the buildingin which water system 12 is housed. This also isolates the high voltagegenerator 40 from other electronic components of the building and thewater system 12, such as sensors 16 which have a separate,uninterruptible power supply or isolation transformer 60. A groundedmetal component 56 is preferably placed in a water reservoir for thewater system 12 (such as sump 54 in the case of a cooling tower).Grounded metal component 56 is preferably a piece of metal or mesh witha large surface area, but other shapes and configurations may be used.This grounded component reduces or eliminates electromagneticinterference through the water. Electromagnetic interference suppressors58 are preferably connected to or clamped on electronic components ofwater system 12, particularly any sensors (such as sensors 16) that willbe used to monitor water qualities—such as conductivity, temperature,and pH. Other grounding devices, such as 52, may be added as necessaryto other reservoirs or piping within water system 12 or connecting watersystem 12 with treatment system 10. In one preferred embodiment,grounding device 52 comprises a screw inserted into a wall of a pipethrough which water in the water system is flowing, with a length ofwire connected at one end to the head of the screw and wrapped aroundthe pipe several times, with the other end connected to ground. Othergrounding devices or configurations may also be used as will beunderstood by those of ordinary skill in the art. Typically, thesegrounding devices will be placed on or near specific types of equipment,such as a corrater (corrosion monitoring system), chemical controller,flow controller, conductivity probe, or will be spaced out throughoutthe water system with 2-4 devices used in most large water systemapplications. These grounding devices serve to protect the components ofwater system 12 and also allow the energy from the multiple groundpoints to be harvested and stored in a capacitor or inductor. Theharvested and stored energy may be used to generate low level energeticfields (electromagnetic or electrochemical) that provide furtherbenefits to the water treatment process. Electromagnetic fields havebeen used to prevent chemical scale formation and have been used toinduce electroporation and ion cyclotron resonance, which have beenshown to have antimicrobial properties. Electrochemical reactions cangenerate areas of localized high and low pH and can induceelectroporation as well. They may also generate low levelelectromagnetic fields locally within the water system without storingthe energy. For example, with a wrapped wire device around a pipe in thewater system as described above, each time a pulse (from the plasma) issinked to ground, a current will flow through the wire loops around thepipe to generate a magnetic field in the water flowing through the pipeat that location.

Treatment system 10 is preferably run using a timer or other controllerdevice in which the system can be activated/deactivated in periodicintervals, preferably around 15 minute intervals, to reduce overallsystem heating and increase efficiency. As the system heats up, moreenergy will be dissipated in the Marx generator 40, which results inmore charging losses and less energy being available for plasmageneration. Allowing the system to cool during periodic deactivationreduces charging losses and increases efficiency. Periodicactivation/deactivation will also allow the ozone from the spark gapchamber to be flushed out on a regular basis and maintain a pulsed arcdischarge over the greater than 5 mm electrode gap. In order to operatethe system safely it is necessary to power the system through a switchbox 45 that features a ground fault circuit interrupt. This emergencystop system will trigger if the current flowing from the device does notmatch the current sinking into the device.

The following are examples wherein a treatment system 10 according tovarious embodiments of the invention were tested.

EXAMPLE 1A Direct Discharge Into an Unprotected System

In the first set of experiments, a pilot cooling tower was used.Components of this experimental system that correspond with the systemsdepicted in FIG. 1 are labeled according to the reference numbers inFIG. 1. A cooling tower (total volume 100 L) water system 12 was chargedwith water and the system was set to circulate. The water chemistry wasmonitored using an Advantage Control system and biological monitoring asperformed using two in-house biological monitoring systems and aChemTrak biological monitor. These systems are typically found or aresimilar to those typically found in larger scale commercial orindustrial cooling tower operations. To incorporate the high voltagegenerator system into the cooling tower, a side-stream flow (stream 18)was pulled from the heat exchanger rack via a mechanical ball valve and12 feet of 0.75 inch diameter clear flexible PVC tubing. This valveallows the system to change flow dynamics based on the specificcomposition of the water being treated. For example, changing the flowrate past the venturi changes how the gas bubbles are distributed intothe water and this in turn can change the form of the plasma generatedat the high voltage discharge electrode. Also volume and flow rate areimportant in terms of treatment of the entire system water forbiological control using directed high voltage discharge becausesuccessful treatment depends not only on the amount of energy beingdelivered, but also the treatment time. Since bacteria are constantlyreplicating in a typical system within a large volume of water, it isimportant to achieve a high enough flow rate through the reactionchamber 36 in order to ensure that the entire volume of system water isrepeatedly treated or cycled through the high voltage discharge zone toincrease total treatment time (the total amount of time a column ofwater with biological constituents in in contact with the high voltagedischarge).

Using this setup on the pilot cooling towers allows for a maximum of 2gpm side-stream flow. This tubing was connected to a plasma chamber 36via a threaded polyethylene barbed fitting. At the outlet of thereaction chamber, 5 feet of clear PVC tubing is used to drain the waterexiting the reaction chamber (stream 50) into the sump 54. None of thegrounding points (such as ground 52 and 56) described with respect to apreferred embodiment above were put in place. The reaction chamber 36was connected to a high voltage generator 40. The unit was activated anda pulsed spark discharge in water with 1,500 μmhos conductivity wasobserved over a 1 cm electrode gap. Immediately upon activating the highvoltage generator 40, flow control relays of water system 12 began toactivate off and on, cutting off power to the water system 12. Theelectronics in the Advantage Controller over loaded and shut the systemdown and the biomonitor output (located on the other side of the roomfrom the high voltage generator 40) overloaded and shut off. FIGS. 2Aand 2B show the electromagnetic fields measured in the water with theplasma unit on in this test embodiment, with water flow and no waterflow with the electromagnetic fields traveling through the water in bothcases. It can be seen that when the water is flowing (FIG. 2A) there isa high resonance electromagnetic pulse penetrating the water circulatingthrough the system. It can be seen that even when the water is notflowing (FIG. 2B) there was still a measurable electromagnetic fieldresulting for the high voltage discharge.

EXAMPLE 1B Direct Discharge Into a Protected System

The experiment of 1A was repeated, but with a multiple ground protectivesystem in place. Grounds were placed in a sump 54 and parts of thetubing (using a screw and wire wrapping as discussed above) throughoutsystem. FIG. 3 shows that there is a significant reduction in theelectromagnetic field in the water. Using the multiple ground system, itis now possible to run the high voltage discharge system for severalhours continuously without causing problems to the electronic controland monitoring equipment used as part of the water system 12.

EXAMPLE 2 Bench Trials for Removal of Microorganisms

Four bench-level studies were conducted to determine the efficacy of anon-thermal plasma discharge in water to inactivate microorganisms. Itis known that a plasma discharge in water will generate active oxygenspecies, UV radiation, and pressure field shock waves all of which caninactivate microorganisms. A plasma discharge can be achieved byincreasing the electric field in a solution beyond its breakdownvoltage. The breakdown voltage is dependent on the conductivity and thedielectric properties of the solution. It has been observed that arelationship exists between the input energy and the log reduction ofthe microorganisms in the system. It has also been documented that theinput energy needed to achieve a one log reduction (known as D-value) inE. coli can vary from 14 J/L to greater than 366 J/L. As for experimentswith certain species of pseudomonas, it has been reported that 85 kJ/Lis the average input energy needed to achieve one log reduction.

In a first experimental set, a rod to cylinder electrode configurationwas placed in a beaker containing 1,600 mL of water (800 mL of tap waterand 800 mL of distilled water). Ozone generated from a Marx generator(from the non-thermal plasma's voltage multiplier) was aerated into asecondary beaker containing 1,600 mL of water (also 800 mL of tap waterand 800 mL of distilled water) (beaker #2). For these tests, Escherichiacoli (E. coli) was utilized because of its high susceptibility toinactivation by directed energy methods. For each of the beakerscontaining 1,600 mL of the described water, 2 mL of a TSB stock solutionwith a known concentration of suspended E. coli was used to inoculateeach of the water filled beakers for a final E. coli concentration of4.65×10⁶ cfu/mL (Test #1) and 4.50×10⁶ cfu/mL. For the plasma onlybeaker test (beaker #1), the cylinder electrode diameter was increasedfrom a ¼ inch (which generated an arc discharge) to a 1 inch size sothat a pulsed corona was generated during the discharge. A purpose ofthis test was to determine which of an arc discharge (which puts moreenergy into the system, which is preferred) or a pulsed corona resultsin the most biological inactivation.

As for the ozone treatment only beaker, ozone was pushed through a Marxgenerator chamber and bubbled into the beaker with the use of anairstone. During the experiments, 25 mL samples were collectedindependently from each beaker at 0 min., 2 min., 4 min., 10 min., 20min., and 30 min. and bioassayed for cfu/mL determination. The resultsof the pulsed corona discharge plasma only test are shown in Table 1below under Test #1.

A second experiment combined the aerated ozone and a rod to cylinderelectrode setup into a single beaker containing 1,600 mL of water (800mL of tap water and 800 mL of distilled water) (Test #2). For this test,2 mL of a TSB stock solution with a known concentration of suspended E.coli was used to inoculate the water filled beaker for a final E. coliconcentration of 6.10×10⁶ cfu/mL. The cylinder electrode diameter ¼ inchso that a pulsed spark (pulsed arc discharge) would be generated in thesolution during discharge and the ozone generated by a Marx generatorwas bubbled into the beaker beneath the electrode setup. During theexperiment, 25 mL samples were collected at 0 min., 10 min., 30 min., 45min., and 60 min. and bioassayed for cfu/mL determination. The resultsare shown in Table 1 below under Test #2.

A third experiment featured a rod to cylinder electrode configurationplaced in a beaker containing 1,600 mL of water (800 mL of tap water and800 mL of distilled water) (Test #3). Ozone generated from a Marxgenerator (from the non-thermal plasma's voltage multiplier) was aeratedinto a secondary beaker containing 1,600 mL of water (again 800 mL oftap water and 800 mL of distilled water). For this study, Escherichiacoli (E. coli) was utilized because of its high susceptibility toinactivation by directed energy methods. For each of the beakerscontaining 1,600 mL of the described water, 2 mL of a TSB stock solutionwith a known concentration of suspended E. coli was used to inoculateeach of the water filled beakers for a final E. coli concentration of3.05×10⁶ cfu/mL and 3.40×10⁶ cfu/mL respectively. Similar to the secondexperiment, the cylinder electrode diameter was lowered so that a pulsedspark (pulsed arc discharge) would be generated in the solution duringdischarge. As for the ozone treatment only beaker, ozone was pushedthrough the Marx generator chamber and bubbled into the beaker with theuse of an airstone. During the experiment, 25 mL samples were collectedindependently from each beaker at 0 min., 10 min., 15 min., 30 min., and45 min. and bioassayed for cfu/mL determination. The results are shownin Table 1 under Test #3.

In a fourth experiment, the aerated ozone was combined with and a rod tocylinder electrode setup into a single beaker containing 2,000 mL ofwater (1,000 mL of tap water and 1,000 mL of distilled water) (Test #4).For this test, 5 mL of a TSB stock solution with a known concentrationof suspended Pseudomonas putida was used to inoculate the water filledbeaker for a final Pseudo. putida concentration of 7.00×10⁷ cfu/mL.Different from the first experiment, the cylinder electrode diameter waslowered so that a pulsed spark (pulsed arc discharge) would be generatedin the solution during discharge and the ozone generated by a Marxgenerator was bubbled into the beaker beneath the electrode setup.During the experiment, 25 mL samples were collected at 0 min., 15 min.,30 min., 45 min., and 60 min. and bioassayed for cfu/mL determination.The results are shown in Table 1.

TABLE 1 Summary of Plasma Effectiveness Studies (Bench-Level Testing)Test 1 Test 2 Test 3 Test 4 (E. Coli) (E. Coli) (E. Coli) (Psuedo.Putida) Plasma Only Plasma + Ozone Plasma Only Study Plasma + OzoneStudy Study Pulsed Spark Study Pulsed Corona Pulsed Spark (Pulsed Arc)Pulsed Spark Discharge in a (Pulsed Arc) Discharge in a (Pulsed Arc)beaker with no Discharge Plus beaker with no Discharge plus Ozone OzoneTreatment Ozone Ozone Treatment Sample Sample Sample Sample 0 min. 0min. 0 min. 0 min. (Control) (Control) (Control) (Control) 6.67 log Log6.69 log Log 6.67 log Log 6.67 log Log (cfu/mL) Reduction (cfu/mL)Reduction (cfu/mL) Reduction (cfu/mL) Reduction  2 min. 0.15 10 min.1.28 10 min. 2.74 15 min. 0.72  4 min. 0.23 30 min. 5.79 15 min. 3.82 30min. 1.46 10 min. 0.40 45 min. 5.14 30 min. 4.20 45 min. 1.55 30 min.0.99 60 min. ≥6.79 45 min. 4.46 60 min. 1.85

Referring to FIG. 4, a field test was also performed using a preferredembodiment of the system and method of the invention. The goal for thisfield test was to install a plasma water treatment system 110 in acooling tower water system 112 that used oxidizing biocides to controlthe microbial population in the water. The cooling tower water system112 had a total volume of 1,400 gallons and was situated at street leveloutside the administrative building of a local University. A controlunit 115 that monitored water flow and water conductivity was used tocontrol the system blow down and chemical feed into the sump 154. Thisunit maintained water conductivity between 900 μmhos and 1500 μmhos. Theplasma treatment system 110 comprises a high voltage generator 140 and aplasma reaction chamber 136. High voltage generator comprises a Marxladder or Marx generator 42 disposed within a spark gap chamber 41within an outer housing 43 that includes a dielectric barrier. Ozone gasstream 130 is withdrawn from spark gap chamber 141 and is injected intoinlet water stream 114 via a venturi 121. Although not used initially inthis test, air 122 and/or reactive gas 126 could also be injected intothe water stream through a micro-bubbler or similar device 120. A tee,mixer, or similar connecting device 129 may be used to infuse stream 124(containing ozone) with micro-bubbles of air and/or reactive gas frommicro-bubbler 120 and provide an inlet into reaction chamber 136.Reaction chamber 136 comprises a sealed, water-tight housing 135surrounded and shielded by an inner dielectric barrier layer 134 a andouter ground shield 134 b. The dielectric barrier 34 a is anon-conductive layer that prevents arcing to the ground layer 34 b,which is a conductive outer layer tied to the ground. Within reactionchamber 136 are disposed a high voltage electrode and a ground electrodewhich generate a plasma discharge within chamber 136 as voltagegenerated in high voltage generator 140 is transmitted to the highvoltage electrode within chamber 136 via wire 138. Another ground 148 isalso disposed in contact with ground layer 134 b surrounding housing135. Reaction chamber 136 in this field test was around 4 inches indiameter. The reaction chamber 136 in this field test was plumbeddirectly into the existing water lines of water system 112. The reactorinlet 129 was connected to the water line 114 from the high pressureside of the pump 113 which was removing the water from the cooling towersump 154. A venturi 121 inserted into the line between the pump 113 andthe reactor 136 was used to draw ozone gas 130 generated by the Marxladder 142 into the water being treated. The treated water 150 exitingthe reaction chamber 136 was returned to the output side of the chillerwhere it circulated back into the cooling tower.

When the system 110 was installed initially, none of the recommendedprecautions or protective measures mentioned in reference to FIG. 1 andtreatment system 10 were in place. The system 110 was installed in closeproximity to the master control system, it was not grounded, there wasno shielding of the controller unit and there were no ferrite beadsaround the sensors leads for EMI suppression. The high voltage generator140 was plugged directly into main electrical outlet in the wall.

To start the process, water stream 114 was introduced into the reactionchamber 136 and the high voltage system 140 was activated. Immediatelythe electromagnetic feedback through the water caused the conductivitymeter on the water system 112 to jump to 6000 μmhos, forcing the watersystem 112 into an immediate blow down mode that resulted in water beingdumped to the drain. Without one or more of the protective measuresreferenced with system 10 of FIG. 1, it would be impossible toeffectively operate a high voltage discharge system in a cooling system.

The set-up of systems 110 and 112 were then reconfigured with the watercontrol unit 170 (used to control various components of the water system112) being isolated within a housing 172 and by clamping ferrite beads158 around the wires leading to the conductivity sensor 116. Housing 172encloses system control unit 170 during operation of system 110, butcomprises an openable door or a removable cover so that the interior maybe accessed for service. Housing 172 is preferably a metal box, butother shielding materials such as plastics, concrete or metal plasticcomposites may also be used. The high voltage generator 140 was moved tothe opposite side of the room from the controller (approximately 12 feetaway, and preferably at least 6 feet away) and the power supply 146 wasswitched from directly connected to the mains to being run through aUPS. The sump 154 in the cooling tower was grounded 156 as was thereturn (treated) water line 150 grounded by 148. When the system 110 wasactivated there was no negative impact on the control system 170 orsensor 116, allowing the cooling tower system 112 to operate normally.

Using this set up, the water treatment system 110 was run for 6 monthswithout the addition of biocide. During the process, ozone gas 130generated in the Marx ladder 142 was introduced into the water enteringthe reaction chamber 136. This produced a fine stream of bubbles at thehigh voltage electrode surface. When the water had a low conductivityaround 900 μmhos this would be sufficient to generate a plasmadischarge, but as the conductivity increased with increasing number ofcycles of concentration, this was no longer adequate to generate aplasma discharge in the reaction chamber. Additional air 122 wasintroduced into the reaction chamber that provided a more robust aircurtain between the ground electrode and the high voltage dischargeelectrode allowing plasma to be generated in water with conductivity inexcess of 1500 μmhos. Once the conductivity reaches a pre-set threshold,usually around 1500 μmhos, the cooling tower or other water system goesinto blow down mode, dumping the high conductivity water to the drainand replacing it with new water (usually fresh water from a municipalsupply, but other water sources with lower conductivity levels may beused).

Referring to FIG. 5, another preferred embodiment of plasma treatmentsystem 210 was tested in a second field trial. System 210 was installedto treat a 2,200 gallon stainless steel/galvanized cooling tower watersystem 212. During this installation, the high voltage generator 240 andthe plasma reactor chamber 236 were shielded within a housing 260 andplaced on the outside wall away from the water control unit 270 andsensors 216 of water system 212. Housing 260 is preferably at least 6feet away from water control unit 270 and sensors 216. Housing 260 ispreferably made of metal, but other materials such as plastic or metalplastic composites may also be used. Housing 260 encloses system 210during operation, but comprises an openable door or a removable cover sothat the interior may be accessed for service. When housing 260 is used,it is not necessary to enclose control unit 170 in a housing (such ashousing 172 used with system 110), but such a housing may also be usedfor added protection of the control unit. The water 214 from the sump254 was circulated through the plasma reactor using a pump 213 that wasplaced directly in to the sump 254 which was grounded 256. The highvoltage generator 240 was connected directly to the main electricaloutlet as power supply 246, but the outlet was on its own breakercircuit. With this set-up, system 210 was able to continuously operatefor 6 months (at which time the cooling system was shut-down for winter,but it is believed the system could have continued operating with thisembodiment of the invention for a longer period if cooling was needed)without any electrical or EMI issues interfering with operation of watersystem 212.

Any combination of protective measures, such as a grounded piece ofmetal or mesh with a large surface area placed within a sump (similar to56), electromagnetic interference suppressors (such as 58), groundedwire wrapped pipe segments or ferrite beads (such as 52 or 158 or 258),a protective housing (such as 260) around the high voltage generator andplasma reaction chamber, a protective housing around the water controlunit (such as 172), locating the high voltage supply and reactionchamber a sufficient distance from the water control unit and sensors,segregated power supply for the high voltage generator (such as anoutlet on its own breaker circuit or a UPS or isolation transformer),and/or segregated power supply for the water control unit or sensors(such as a separate UPS or isolation transformer) may be used with anytreatment system according to the invention to protect the water systemcomponents from any interference or damage and to permit the treatmentsystem to operate continuously for extended periods of time. Anycombination of grounding devices may also be used with any treatmentsystem according to the invention to harvest (and to store usingcapacitors or inductors) excess energy generated by the treatment systemand to generate low level energetic fields (electromagnetic orelectrochemical) that provide further benefits to the water treatmentprocess.

References herein to water systems include any type of flowing watersystem, including industrial, commercial, and residential, that requiresperiodic treatment to control or eliminate growth of microbiologicalspecies. Water flowing through the water system may contain contaminantsor chemical or biological treatment agents. The components depicted inthe figures are not drawn to scale but are merely intended asrepresentations of the various components used in preferred embodimentsof treatment systems according to the invention and water systems withwhich those treatment systems are used. Additionally, certain componentsof the water systems depicted in the figures may be in other locationsrelative to other components of the water systems and the systems of theinvention than as depicted in the drawings. Those of ordinary skill inthe art will appreciate upon reading this specification, thatmodifications and alterations to the system and methods for treatingflowing water with a plasma discharge and ozone while protecting thecomponents of the water systems may be made within the scope of theinvention and it is intended that the scope of the invention disclosedherein be limited only by the broadest interpretation of the appendedclaims to which the inventors are legally entitled.

What is claimed is:
 1. A method for treating water in a flowing watersystem with a plasma discharge, the method comprising: diverting atleast a portion of water from the flowing water system to flow through areaction chamber comprising an inlet in fluid communication with theflowing water system to receive the diverted portion of water, anoutlet, a body, a high voltage electrode at least partially disposedwithin the body, and a ground electrode at least partially disposedwithin the body; generating the plasma discharge in the diverted portionof water flowing through the reaction chamber body to treat that portionof water by supplying voltage to the high voltage electrode; optionallysupplying one or more gases to the diverted portion of water in the bodyor upstream of the body; protecting one or more electronic components inthe flowing water system from electromagnetic radiation or interference;and wherein at least a portion of the high voltage electrode contactsthe diverted portion of water in the body while voltage is beingsupplied.
 2. The method of claim 1 wherein the protecting step comprisesproviding one or more ground devices connected to components of theflowing water system.
 3. The method of claim 1 further comprisinggenerating the voltage supplied to the high voltage electrode in a highvoltage generator comprising a Marx ladder.
 4. The method of claim 3wherein the protecting step comprises isolating a power supply to thehigh voltage generator from other electronic components of the flowingwater system by using an isolation transformer, an uninterruptible powersupply, or separate breaker circuits.
 5. The method of claim 3 whereinthe protecting step comprises one or more of the following: connectingone or more electromagnetic interference suppressors to one or moreelectronic components of the flowing water system, segregating a firstpower supply for the one or more electronic components of the flowingwater system from a second power supply for the high voltage generatorand connecting one or more grounding devices to one or more pipesegments or to a sump in the flowing water system.
 6. The method ofclaim 3 further comprising blowing air over electrodes in the highvoltage generator.
 7. The method of claim 1 wherein the voltage suppliedto the high voltage electrode exceeds 200 kV.
 8. The method of claim 1wherein the water is treated to remove biological contaminants and nobiocide is added to the water while the water is being treated with theplasma discharge.
 9. The method of claim 1 wherein the plasma dischargegenerating step is periodically repeated.
 10. The method of claim 1further comprising returning the treated portion of water back to theflowing water system.
 11. A method for treating water in a flowing watersystem with a plasma discharge, the method comprising: diverting atleast a portion of water from the flowing water system to flow through areaction chamber comprising an inlet in fluid communication with theflowing water system to receive the diverted portion of water, anoutlet, a body, a high voltage electrode at least partially disposedwithin the body, and a ground electrode at least partially disposedwithin the body; generating the plasma discharge in the diverted portionof water flowing through the reaction chamber body to treat that portionof water by supplying voltage to the high voltage electrode; optionallysupplying one or more gases to the diverted portion of water in the bodyor upstream of the body; protecting one or more electronic components inthe flowing water system from electromagnetic radiation by connectingone or more electromagnetic interference suppressors to one or moreelectronic components of the flowing water system or connecting one ormore grounding devices to one or more pipe segments or to a sump in theflowing water system, or a combination thereof; and wherein at least aportion of the high voltage electrode contacts the diverted portion ofwater in the body while voltage is being supplied.
 12. The method ofclaim 11 wherein the one or more grounding devices comprise wire wrappedaround a pipe in the flowing water system.
 13. The method of claim 11wherein the one or more grounding devices comprise a grounded piece ofmetal placed in a sump of the flowing water system.
 14. The method ofclaim 11 wherein the flowing water system is a cooling tower or chilledloop system and wherein the one or more components comprises aconductivity meter.
 15. A method for treating water in a flowing watersystem with a plasma discharge, the method comprising: diverting atleast a portion of water from the flowing water system to flow through areaction chamber comprising an inlet in fluid communication with theflowing water system to receive the diverted portion of water, anoutlet, a body, a high voltage electrode at least partially disposedwithin the body, and a ground electrode at least partially disposedwithin the body; generating the plasma discharge in the diverted portionof water flowing through the reaction chamber body to treat that portionof water by supplying voltage to the high voltage electrode; capturingozone produced by the voltage generating step and wherein the ozone issupplied to the diverted portion of water in the body or upstream of thebody; optionally supplying one or more gases other than ozone to thediverted portion of water in the body or upstream of the body; andwherein at least a portion of the high voltage electrode contacts thediverted portion of water in the body while voltage is being supplied.16. The method of claim 15 further comprising generating the voltagesupplied to the high voltage electrode in a high voltage generatorcomprising a Marx ladder.
 17. A method for treating water in a flowingwater system with a plasma discharge, the method comprising: divertingat least a portion of water from the flowing water system to flowthrough a reaction chamber comprising an inlet in fluid communicationwith the flowing water system to receive the diverted portion of water,an outlet, a body, a high voltage electrode at least partially disposedwithin the body, and a ground electrode at least partially disposedwithin the body; generating the plasma discharge in the diverted portionof water flowing through the reaction chamber body to treat that portionof water by supplying voltage to the high voltage electrode; supplyingone or more gases to the diverted portion of water in the body orupstream of the body; wherein at least a portion of the high voltageelectrode contacts the diverted portion of water in the body whilevoltage is being supplied; wherein the flowing water system is arecirculating system and a conductivity level of the water in therecirculating water system increases as it recirculated; and wherein anamount of gas supplied to the diverted portion of water in the body orupstream of the body is increased when the conductivity level reaches orexceeds a predetermined threshold.
 18. A method for treating water in aflowing water system with a plasma discharge, the method comprising:diverting at least a portion of water from the flowing water system toflow through a reaction chamber comprising an inlet in fluidcommunication with the flowing water system to receive the divertedportion of water, an outlet, a body, a high voltage electrode at leastpartially disposed within the body, and a ground electrode at leastpartially disposed within the body; generating the plasma discharge inthe diverted portion of water flowing through the reaction chamber bodyto treat that portion of water by supplying voltage to the high voltageelectrode; supplying one or more gases to the diverted portion of waterin the body or upstream of the body; wherein at least a portion of thehigh voltage electrode contacts the diverted portion of water in thebody while voltage is being supplied; wherein the gas is supplied to thediverted portion of water upstream of the inlet using a venturi system;and wherein a flow rate of the diverted portion of water is adjusted asit flows past the venturi.
 19. A method for treating water in a flowingwater system with a plasma discharge, the method comprising: divertingat least a portion of water from the flowing water system to flowthrough a reaction chamber comprising an inlet in fluid communicationwith the flowing water system to receive the diverted portion of water,an outlet, a body, a high voltage electrode at least partially disposedwithin the body, and a ground electrode at least partially disposedwithin the body; generating the plasma discharge in the diverted portionof water flowing through the reaction chamber body to treat that portionof water by supplying voltage to the high voltage electrode; generatinga magnetic field in the water in the flowing water system by connectingwire to piping in the flowing water system and to a ground and allowingcurrent to flow through the wire; optionally supplying one or more gasesto the diverted portion of water in the body or upstream of the body;and wherein at least a portion of the high voltage electrode contactsthe diverted portion of water in the body while voltage is beingsupplied.
 20. The method of claim 19 further comprising capturing excessenergy produced in the plasma discharge generating step to provide thecurrent to the wire.